NASA looks for antimatter. It’s not just some sci-fi idea?

Astronauts from the space shuttle Endeavour recently attached the Alpha Magnetic Spectrometer, or AMS, to the International Space Station. It will attempt to detect the presence of antimatter in outer space. Since the device has the potential to change the way we think about the universe, this is a good time to brush up on what, exactly, antimatter is.

In the 1920s, British physicist Paul Dirac was trying to make Einstein’s special relativity principle jibe with some of the rules of quantum mechanics — a mathematical system that explains the behavior of small particles. No matter how many times Dirac ran his equations, he couldn’t eliminate a pesky negative sign that he thought didn’t belong there. Dirac ultimately decided the negative sign wasn’t a mistake, but a revelation. For the calculations to work, there had to be an undetected particle with the same weight as a negatively-charged electron — one of the basic building blocks of matter — but with a positive charge. Dirac thus became the first physicist to prove, albeit theoretically, that antimatter existed.

Four years later, Carl Anderson, a 27-year-old graduate student at the California Institute of Technology, detected the positively charged electron in a lab experiment by observing its trail and dubbed it the positron. Both Dirac and Anderson would go on to win the Nobel prize in physics.

Since Anderson’s experiments, scientists have discovered several other forms of antimatter. There’s the antiproton, a negatively charged proton, and the antineutron. (Neutrons have no charge, but the negative of zero is zero, so the theory still holds. Just go with it.) And there are even smaller antiparticles.

Anderson’s experiments might not have been the first time antimatter was created in a lab. His detection methods were the innovation. You see, antimatter and matter don’t get along very well: When a particle and its antiparticle meet, both are annihilated, releasing a bunch of energy. So, any antimatter that appears on Earth disappears almost immediately. Using a device called a cloud chamber, Anderson managed to identify the fleeting traces of the particles before they vanished.

Once the existence of antimatter was proven, a world of potential experiments opened up. At this very moment, scientists at Fermilab in Illinois and CERN, the European Organization for Nuclear Research, are poking and prodding at antimatter particles trying to answer a bunch of fundamental questions.

How fundamental?

“If we find an unexpected difference between particles and antiparticles,” says Harvard physicist Gerald Gabrielse, “our most fundamental description of reality [quantum mechanics] could be wrong, and, the implications would ricochet through all of our theories. Every physical law is potentially at stake.”

Do the physicists have your attention? Now here’s how they make the stuff, er . . . anti-stuff.

“We take a proton beam and slam it into a target,” says Keith Gollwitzer, who works with antiprotons at the Illinois laboratory. “Off comes a series of particles and antiparticles, some of which are antiprotons that can be captured electrically and magnetically.”